High-speed permanent magnet synchronous electric motor for vacuum cleaner

Abstract

The present invention relates to the technical field of electric motors, and specifically relates to a high-speed permanent magnet synchronous electric motor for a vacuum cleaner. The high-speed permanent magnet synchronous electric motor comprises an electric motor housing, wherein a stator core is provided in the electric motor housing; a permanent magnet is concentrically provided inside the stator core; a rotor core is concentrically provided in the permanent magnet; the stator core has a three-slot structure; the permanent magnet is a bonded neodymium-iron-boron magnetic ring, and the permanent magnet is two-pole magnetized; the ratio of the outer diameter of the magnetic ring to the outer diameter of the stator core is between 0.2 and 0.4; and the difference between the inner radius of the stator core and the outer radius of the permanent magnet is between 0.2 mm and 0.5 mm. The device improves the efficiency of the electric motor, and solves the problems of severe rotor heating and the high cost of a sintered neodymium-iron-boron permanent magnet.

Description

A high-speed permanent magnet synchronous motor for vacuum cleaners Technical Field

[0001] This invention relates to the field of motor technology, specifically a high-speed permanent magnet synchronous motor for vacuum cleaners. Background Technology

[0002] Existing household DC handheld vacuum cleaners generally use high-speed permanent magnet synchronous motors. Compared to brushed motors, high-speed permanent magnet synchronous motors are smaller, lighter, and have a longer lifespan, while also boasting higher speeds and power densities. These motors typically operate at speeds exceeding 90,000 rpm, or a mechanical rotational frequency exceeding 1,500 Hz. They typically employ space vector control to generate sinusoidal current for motor operation, aiming to reduce vibration and noise and improve operational smoothness. A circuit diagram is shown in Figure 2. When using space vector control, the switching frequency of the power switches in the three-phase inverter bridge needs to be a certain multiple higher than the motor's rotational frequency to obtain a sinusoidal current with fewer harmonics. Due to the switching frequency limitations of the power switches, these motors typically employ a design that minimizes the number of pole pairs, using two-pole (one-pole) permanent magnets. This design ensures that the motor's rotational frequency equals its mechanical rotational frequency, reducing the need for high switching frequencies in the inverter bridge power switches. The motor's rotational frequency is calculated by multiplying its mechanical rotational frequency by the number of pole pairs.

[0003] The disadvantages of the existing design are as follows: 1. Sintered NdFeB magnets have high electrical conductivity, typically around 700,000 Siemens per meter. The rotational frequency of such motors and the switching frequency of the power switching transistors are both very high, resulting in a high-frequency changing magnetic field in the air gap. Therefore, sintered NdFeB magnets will induce a large amount of eddy current losses in such a high-frequency changing magnetic field. This loss not only reduces motor performance and efficiency but also increases the risk of rotor demagnetization at high temperatures. 2. Sintered NdFeB magnets have a high rare earth content, complex manufacturing process, and high cost. 3. Sintered NdFeB magnets are easily broken, so they usually require a non-magnetic sheath for protection. This sheath occupies about 0.25mm of the motor air gap. This results in an excessively large motor air gap, reducing the motor's power density. Summary of the Invention

[0004] To address the problems described above, this invention provides a high-efficiency, high-speed permanent magnet synchronous motor for vacuum cleaners. This device solves the problems of high cost of permanent magnets, severe rotor overheating, and decreased motor performance.

[0005] To solve the above problems, the following technical solutions are provided:

[0006] The present invention discloses a high-speed permanent magnet synchronous motor for a vacuum cleaner, comprising a motor housing, a stator core having a three-slot structure, a permanent magnet concentrically arranged inside the stator core, and a rotor shaft concentrically arranged inside the permanent magnet. The permanent magnet is a bonded neodymium iron boron magnetic ring, the bonded neodymium iron boron being a two-pole magnet. The ratio of the outer diameter of the magnetic ring to the outer diameter of the stator core is between 0.2 and 0.4. The actual air gap of the motor (the difference between the inner radius of the stator core and the outer radius of the bonded neodymium iron boron magnetic ring) is between 0.2 mm and 0.5 mm.

[0007] In the above solution, the sintered NdFeB magnetic ring is replaced by a bonded NdFeB magnetic ring. The permanent magnet is no longer a conductive material. There is no high-frequency eddy current loss during operation, resulting in less heat generation and lower temperature. This solves the problem of motor rotor overheating, improves motor efficiency, and reduces the risk of rotor permanent magnet demagnetization due to overheating.

[0008] The stator core has a three-slot structure, providing ample winding space, which reduces the winding current density and decreases the winding copper loss of the motor.

[0009] The permanent magnet is a two-pole material and is a bonded neodymium iron boron material with low remanence (the remanence is usually only about 0.65 Tesla). This reduces the electric frequency of the motor and the magnetic flux density in the iron core, thereby significantly reducing the loss of the motor iron core.

[0010] The above solution improves motor efficiency and energy conversion efficiency by removing the rotor sleeve and reducing the air gap, thereby reducing energy waste and environmental pollution. The remanence of bonded NdFeB magnets is approximately 0.65 Tesla, only about half that of sintered NdFeB magnets. However, bonded NdFeB magnets manufactured using high-strength adhesives and appropriate processes have significantly higher tensile strength than sintered NdFeB magnets. Therefore, the rotor sleeve can be removed, greatly reducing the actual air gap of the motor. This design reduces the gap between the outer circle of the permanent magnet and the inner circle of the stator core from approximately 0.85 mm to 0.2 mm to 0.5 mm. This design compensates for the power density loss caused by the reduced remanence of the permanent magnet by reducing the air gap.

[0011] In the above solution, the ratio of the outer diameter of the bonded NdFeB magnetic ring to the outer diameter of the stator core is set between 0.2 and 0.4, achieving optimal cost-effectiveness for the motor. If the outer diameter of the magnetic ring is less than 0.2 times the outer diameter of the stator core, the amount of permanent magnet material used is too small, resulting in insufficient motor output capacity. If the outer diameter of the magnetic ring is greater than 0.4 times the outer diameter of the stator core, the magnetic ring thickness is too large, requiring a protective sleeve to protect the magnetic ring, which would prevent the reduction of the actual air gap in the motor.

[0012] The stator core includes a stator yoke and three stator teeth. Each stator tooth is evenly arranged circumferentially along the inner wall of the stator yoke, and a stator coil is provided on the stator tooth.

[0013] The above solution has the following advantages:

[0014] 1. A high-speed permanent magnet synchronous motor for a vacuum cleaner according to the present invention includes a motor housing, a stator core disposed inside the motor housing, a permanent magnet concentrically disposed inside the stator core, and a rotor shaft concentrically disposed inside the permanent magnet. The permanent magnet is a bonded neodymium iron boron magnetic ring. The bonded neodymium iron boron magnetic ring is a non-conductive material and has no eddy current loss in a high-frequency alternating magnetic field. Therefore, it generates less heat during operation, which greatly improves the efficiency and reliability of the motor.

[0015] 2. This design adopts a two-pole, three-slot structure. The motor has a lower electrical frequency when rotating at high speed, which reduces the loss of the motor core. The three-slot structure gives the motor a larger winding area, which reduces the current density of the motor winding and reduces the copper loss of the motor winding.

[0016] 3. In this solution, a suitable ratio of the outer diameter of the magnetic ring to the outer diameter of the stator is selected. By utilizing the high tensile stress of the bonded NdFeB magnetic ring, the sheath on the surface of the magnetic ring is removed, reducing the actual air gap of the motor to 0.2mm to 0.5mm. This greatly improves the power density of the motor, compensates for the lack of motor power caused by the low residual magnetism of the bonded NdFeB magnetic ring, and significantly reduces the cost. Attached Figure Description

[0017] Figure 1 is a schematic diagram of the stator and rotor of a high-speed permanent magnet synchronous motor for a vacuum cleaner.

[0018] Figure 2 is a schematic diagram of a control circuit for a high-speed permanent magnet synchronous motor used in a vacuum cleaner;

[0019] Figure 3 is a schematic diagram of the magnetic circuit of a sintered NdFeB motor with a 0.85mm air gap;

[0020] Figure 4 is a schematic diagram of the magnetic circuit of a NdFeB motor with a 0.3mm air gap bonding.

[0021] Figure 5 is a schematic diagram comparing the working efficiency of a sintered NdFeB motor with a 0.85mm air gap and a bonded NdFeB motor with a 0.3mm air gap.

[0022] Figure 6 is a schematic diagram comparing the stator iron loss, winding copper loss and permanent magnet eddy current loss of a 0.85mm air gap sintered NdFeB motor and a 0.3mm air gap bonded NdFeB motor.

[0023] Explanation of reference numerals in the attached diagram: 1. Stator core; 101. Stator yoke; 102. Stator tooth; 2. Permanent magnet; 3. Rotor shaft; 4. Stator coil. Detailed Implementation

[0024] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] As shown in Figure 1, a high-speed permanent magnet synchronous motor for vacuum cleaners according to the present invention includes a motor housing, a stator core 1 disposed inside the motor housing, a permanent magnet 2 concentrically disposed inside the stator core 1, and a rotor shaft 3 concentrically disposed inside the permanent magnet 2. The permanent magnet 2 is a bonded neodymium iron boron magnetic ring. The bonded neodymium iron boron magnetic ring is a non-conductive material, has no eddy current loss, and operates at a low temperature, which greatly improves the performance and reliability of the motor.

[0026] The stator core 1 has a three-slot structure, which increases the winding area, reduces the winding current density, and reduces the copper loss of the winding. The permanent magnet 2 is a two-pole structure, which reduces the electrical frequency and makes the stator core loss even smaller.

[0027] The ratio of the outer diameter of the permanent magnet 2 to the outer diameter of the stator core 1 is set between 0.2 and 0.4. This ensures that there is sufficient magnetic field strength to obtain high power density of the motor, while also ensuring that the outer diameter of the permanent magnet 2 is not too large and the tensile stress during high-speed operation is not too high. Meanwhile, because permanent magnet 2 uses bonded NdFeB material, its tensile strength is significantly higher than that of sintered NdFeB. Therefore, the original protective sleeve was removed from the periphery of permanent magnet 2, thereby controlling the actual air gap of the motor between 0.2mm and 0.5mm. The smaller motor air gap greatly increases the power density of the motor, allowing the motor to still achieve a considerable power density even when using bonded NdFeB material with only almost half the remanence of sintered NdFeB. Due to its low remanence, bonded NdFeB results in a smaller radial force wave in the motor air gap, reducing noise generation. The vacuum cleaner operates with significantly lower noise, improving the user experience. Bonded NdFeB magnetic rings contain less rare earth elements than sintered NdFeB magnetic rings, and the manufacturing process is simpler, thus reducing the cost by nearly half.

[0028] The stator core 1 includes a stator yoke 101 and three stator teeth 102. Each stator tooth 102 is evenly arranged circumferentially along the inner wall of the stator yoke 101, and a stator coil 4 is provided on the stator tooth 102.

[0029] In the background technology, motor A, with a two-pole, three-slot design and a 0.85mm air gap, uses sintered NdFeB magnets as the permanent magnet 2. Motor B, with a two-pole, three-slot design and a 0.3mm air gap, uses bonded NdFeB magnet rings as the permanent magnet 2. Comparing the two, motor B has a higher operating efficiency than motor A, as shown in Figure 5. However, comparing the two, motor B's stator core loss is significantly lower than motor A's stator core loss, motor B's winding copper loss is slightly higher than motor A's, and motor B's rotor eddy current loss is significantly lower than motor A's permanent magnet 2 eddy current loss, as shown in Figure 6. Therefore, motor B, using bonded NdFeB magnet rings with a small air gap as the permanent magnet 2, is superior to motor A, which uses sintered NdFeB magnet rings as the permanent magnet 2.

[0030] In the description of this invention, it should be understood that the terms "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. In the description of this invention, unless otherwise specified and limited, it should be noted that the terms "installed," "connected," and "linked" should be interpreted broadly. For example, they can refer to mechanical or electrical connections, or internal connections between two elements; they can be direct connections or indirect connections through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms according to the specific circumstances.

[0031] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A high-speed permanent magnet synchronous motor for a high-efficiency vacuum cleaner, characterized in that, The device includes a motor housing, inside which a stator core (1) is provided. The stator core (1) has a three-slot structure. A permanent magnet (2) is concentrically arranged inside the stator core (1). A rotor shaft (3) is concentrically arranged inside the permanent magnet (2). The permanent magnet (2) is a bonded neodymium iron boron magnetic ring. The magnetic ring (2) has two magnetization poles. The ratio of the outer diameter of the magnetic ring (2) to the outer diameter of the stator core (1) is between 0.2 and 0.

4. The difference between the inner radius of the stator core (1) and the outer radius of the permanent magnet (2) is between 0.2 mm and 0.5 mm.

2. The high-speed permanent magnet synchronous motor for a vacuum cleaner as described in claim 1, characterized in that, The permanent magnet (2) is a bonded neodymium iron boron cylindrical magnetic ring with two non-conductive poles.

3. The high-speed permanent magnet synchronous motor for a vacuum cleaner as described in claim 1, characterized in that, The stator core has a structure in which three stator teeth (102) and three slots are arranged alternately.

4. A high-speed permanent magnet synchronous motor for a vacuum cleaner as described in claim 1, characterized in that, The stator core (1) includes a stator yoke (101) and three stator teeth (102). Each stator tooth (102) is evenly arranged circumferentially along the inner wall of the stator yoke (101), and a stator coil (4) is provided on the stator tooth (102).

5. A high-speed permanent magnet synchronous motor for a vacuum cleaner as described in claim 1, characterized in that, The rated power of the motor ranges from 100W to 1,500W.

6. A high-speed permanent magnet synchronous motor for a vacuum cleaner as described in claim 1, characterized in that, The rated speed of the motor is 50,000 rpm / min to 350,000 rpm / min.

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